BirdAnalyst
Species · Iowa · BBS 2025 Release · 1966–2024

Black-billed Cuckoo Population Trend in Iowa

All statesGeneralists

Black-billed Cuckoo in Iowa has fallen sharply: down 75% on the route-weighted index since 1969.

-75%Since 1969TrendPercent change in the route-weighted abundance index between a smoothed baseline window and the most recent one. It tracks direction, not absolute population.Full methodology →
36Routes In StateSurvey routesHow many standard-protocol BBS routes contributed counts. More routes means a steadier, better-sampled index; very thin coverage is suppressed.Full methodology →
49YearsYears surveyedNumber of years with at least one standard-protocol run in this geography. A longer record makes the trend more reliable.Full methodology →

Notable Black-billed Cuckoo Trends in IowaNotable signalsLong-arc shifts the engine flags automatically — sustained declines or increases large enough to stand out from year-to-year noise.Full methodology →

long arc declinecomputed indexTrend sourceWhether the figure is our own computed route-weighted index or an official USGS modeled estimate. The current build labels every trend as computed.Full methodology →

Black-billed Cuckoo has fallen sharply in Iowa: down 75% on the route-weighted index since 1969.

Black-billed Cuckoo Population Forecast in Iowa

If the recent trend holds, Black-billed Cuckoo in Iowa is projected to fall about 29% by 2024 — from 0.08 in 2019 to a central estimate of 0.06 (95% range 0.00–0.55). A 5-year backtest shows a typical error of ±125.6%, with 100% of held-out values landing inside the 95% band.

-29%Change by 2024TrendPercent change in the route-weighted abundance index between a smoothed baseline window and the most recent one. It tracks direction, not absolute population.Full methodology →
0.06Projected 2024 indexProjected indexThe central forecast of the abundance index if the recent trend continues. A projection of the current trajectory, not a prediction.Full methodology →
0.00–0.5595% range95% rangeThe 95% uncertainty band around the projection at the forecast horizon. The true value should land inside it most of the time.Full methodology →
±125.6%Backtest errorBacktest errorTypical error when we hold out the most recent years, forecast them, and compare to what actually happened. Lower means a more trustworthy projection.Full methodology →
If the recent trend holds, Black-billed Cuckoo in Iowa is projected to fall about 29% by 2024 — from 0.08 in 2019 to a central estimate of 0.06 (95% range 0.00–0.55). A 5-year backtest shows a typical error of ±125.6%, with 100% of held-out values landing inside the 95% band.19672024
Projection of the recent trend (dashed) with 80/95% bands — a projection, not a prediction. Habitat, climate, and land use are not modeled.
YearProjected indexProjected indexThe central forecast of the abundance index if the recent trend continues. A projection of the current trajectory, not a prediction.Full methodology →95% low95% rangeThe 95% uncertainty band around the projection at the forecast horizon. The true value should land inside it most of the time.Full methodology →95% high95% rangeThe 95% uncertainty band around the projection at the forecast horizon. The true value should land inside it most of the time.Full methodology →
20200.100.000.59
20210.090.000.58
20220.080.000.57
20230.070.000.56
20240.060.000.55

Black-billed Cuckoo Survey Routes in Iowa

Routes recording Black-billed Cuckoo in Iowa.
Recent countThe raw number of individuals recorded on this route in its most recent survey year. A single-route tally, not a trend.Full methodology →
Wales320181977
Washta320031973
Melrose220101978
College Spgs219921968
Cedar Valley219921968
Prairieburg219821972
Zearing219941971
Rock Valley220011970
Mt Hamill120151969
Exline120071985
Bedford120181989
Bryant119921968
West Liberty120171972
Brooklyn120051967
Williamsburg119971967
Red Rock120011970
Desmoines119781978
Panther120091992
Washington120051973
Neola120081968
Maquoketa120191967
Alice119971970
Hudson120061970
Dinsdale120051982
Kanawha120011967

Black-billed Cuckoo Population Trend in Other States

alabamaarkansascoloradoconnecticutdelawaregeorgiaidahoillinoisindianakansaskentuckymainemarylandmassachusettsmichiganminnesotamissourimontananebraskanew-hampshirenew-jerseynew-yorknorth-carolinanorth-dakotaohiooklahomapennsylvaniarhode-islandsouth-dakotatennesseetexasvermontvirginiawest-virginiawisconsinwyoming

Source: USGS North American Breeding Bird Survey, retrieved 2026-05-22.